It's called a heat riser valve, and it's important for keeping the fuel vapor from condensing back into liquid gasoline on a cold start. The engine will run lousy when it's cold if exhaust gas isn't directed up against the bottom of the intake manifold during warmup. Try tapping the shaft back and forth (not rotating it) with a medium-sized hammer until the rust breaks loose. Heat is also your friend- - - -either work with the shaft while the manifold is hot from running the engine, or use a torch to heat the area around the shaft before working with it. I like KROIL- - - -been using it for 40 years, and I haven't found a better penetrating oil yet.

www.kanolabs.com

Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!